They usually result from a gold-coated fiber
segment for which the core-guided light is brought into contact with the surrounding medium. Recently,
SPR excitation was achieved with tilted fiber Bragg gratings (TFBGs) photo-imprinted in the fiber core
and surrounded by a thin gold layer. These gratings probe the surrounding medium with near-infrared
narrowband (100 pm linewidth) resonances, which enhances both the penetration depth of the evanescent
field in the external medium and the wavelength resolution of the interrogation. They also
constitute the unique configuration able to probe all the fiber cladding modes individually, with high
Q-factors. We use these unique spectral features in this work to target and detect extracellular membrane
receptors in native membranes of different human epithelial cell lines. A differential diagnosis has
been demonstrated between two systems, a cell line with overexpressed membrane receptors (the positive
control) and another cell line with a low number of these receptors (a negative control). Such
results bring an important step towards the demonstration of in situ diagnosis